1. A control unit for a rotary evaporator for evaporating a substance contained in an initial substance, the rotary evaporator having an evaporation flask for receiving the initial substance, a heating device adapted to heat the substance to obtain a vaporized substance, a condenser adapted to condense the vaporized substance to obtain a re-liquefied substance, a collection container adapted to receive the re-liquefied substance and at least one pressure-generating device adapted to generate a low pressure and/or an excess pressure, wherein the control unit is configured and/or programmed to control the rotary evaporator such that an excess pressure is generated at least within the collection container in order to remove the re-liquefied substance and/or an excess pressure is generated at least within the evaporation flask in order to remove residues of the initial substance, wherein the initial substance is a substance mixture of different components and at least two first conduit portions of the rotary evaporator are provided for supplying the initial substance in a metered manner, and wherein the control unit is configured and/or programmed to control shut-off devices of the rotary evaporator provided at and/or between the conduit portions and metering the different components of the initial substance in order to provide for an automatic supply of the initial substance in a metered manner, so that the initial substance is produced in the evaporation flask itself.